(CBS/AP)-- Authorities say the gunman who killed two people and himself in a shooting rampage at an Oregon mall was 22 years old and used a stolen rifle from someone he knew.

Clackamas County Sheriff Craig Roberts says that Jacob Tyler Roberts had armed himself with an AR-15 semiautomatic rifle and had several fully loaded magazines.

Ore. mall evacuated after shooting.Roberts says the rifle jammed during the 22-year-old's attack, but he managed to get it working again.

The chief says authorities don't yet have a motive.

A U.S. law enforcement official has told The Associated Press the shooter did not have a criminal record. The official spoke on condition of anonymity because he was not authorized to discuss details of an ongoing criminal investigation.

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